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Using XMLTextReader to Read XML Data
by Charles Carroll

The XMLTextReader can be much easier than the DOM or SAX to locate and filter data. It is ideal for large files since unlike the DOM it never loads an entire file in memory. Its design is so you can read through the file and when you notice items you want to grab you respond appropriately.

Here is code to read any XML File with an XMLTextReader object and see what types it emits. This toy program displays all the emitted types in a table for ANY XML FILE in this case the sample file @
http://www.learnasp.com/experiments/data/favebooks.xml
but you can easily run this on any XML file to know exactly what types an XMLTextReader will emit.

   filename=/experiments/booksfave/xmltextreader.aspx

<Test Script Below>


<%@trace="false" debug="true" %>
<%@ Import Namespace="System.XML"%>
<%@ Import Namespace="system.xml.xmlnodetype"%>
<%@ Import Namespace="system.drawing"%>
<script language="VB" runat="server">
Sub Page_Load(S As Object, E As EventArgs)
    trace.tracemode=TraceMode.SortByTime
    
    DIM Xmltr1 as XMLTextReader
    
    TRY
        Xmltr1=new XMLtextReader(server.mappath("/experiments/data/favebooks.xml"))
        DIM strTemp as string

    
        DO WHILE Xmltr1.Read()
            trace.warn ("Value", Xmltr1.Value)
            'trace.write ("Text", Xmltr1.Text)
            strTemp  = "NodeType=" & Xmltr1.NodeType.ToString()
            IF  Xmltr1.Name<>string.empty
                strTemp &= ";Name=" & Xmltr1.Name
            END IF
            IF  Xmltr1.LocalName<>string.empty
                strTemp &= ";LocalName=" & Xmltr1.LocalName
            END IF
            IF  Xmltr1.NamespaceURI<>string.empty
                strTemp &= ";NamespaceURI=" & Xmltr1.NamespaceURI
            END IF
            trace.write("",strTemp)
            TableCellsAdd(XMLtr1.Value,strTemp)
            
            IF Xmltr1.hasattributes
                trace.write ("attributecount", Xmltr1.attributecount)
                DO WHILE Xmltr1.MoveTonextAttribute()
                    trace.write ("value;name",Xmltr1.name & ";" & Xmltr1.value)
                    TableCellsAdd("attribute named <b>" & XMLtr1.Name & "</b>;value=<font color='red'>" & XMLtr1.Value & "</font>","")
                LOOP
            END IF
        LOOP
    
    CATCH ex1 as exception
    
    FINALLY
        Xmltr1.Close()
        
    END TRY
End Sub

Sub TableCellsAdd(strParm1 as string,strParm2 as string)
        static intCellcounter as integer
        DIM cl1,cl2 as tablecell
        DIM rw1 as tablerow 

        cl1=new tablecell
        cl2=new tablecell
        cl1.controls.add(new literalcontrol(strParm1))
        cl2.controls.add(new literalcontrol(strParm2))
        rw1=new tablerow
        rw1.cells.add(cl1)
        rw1.cells.add(cl2)
        intCellCounter+=1
        IF intCellCounter MOD 2 = 0
            rw1.BackColor=Color.FromName("Silver")
        END IF
        tblXMLDetails.rows.add(rw1)        
End Sub

</script>
<html><head>
<title>XML Demo</title>
</head>
<body bgcolor="#FFFFFF">
<form runat="server">
<ASP:placeholder id="plcErr" runat="server" />
See The Trace For More Details
<AsP:Table id="tblXMlDetails" runat="server" />
<ASP:placeholder id="plcEndofPage" runat="server" />
</form>
</body></html>

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